Q: How many animals are used each year in U.S. laboratories for biomedical research?A: It is estimated that more than 25 million vertebrate animals (animals with a skeleton made of bone) are used annually in research, testing, and education in the United States. Unfortunately, no accurate and comprehensive figures are available on how many animals are used—or for what purposes—in the United States or worldwide. The U.S. Department of Agriculture does compile annual statistics on the number of dogs, cats, primates, rabbits, hamsters and guinea pigs (as well as some wild animals and, more recently, farm animals) used in research in the United States. For USDA statistics on animal use, see Animal Care Reports here.

Q: What is the most commonly used species of animal in biomedical research? A: Animals used for research include (in decreasing order of frequency): mice, rats, birds, rabbits, guinea pigs, hamsters, farm animals (including pigs and sheep), dogs, primates (including monkeys and chimpanzees), and cats.

Frogs and fish are also widely used, but current statistics on their use are unavailable.

It is important to note the most common laboratory animals—rats and mice bred for research, who make up 85–90 percent of all animals used—are not counted in the annual statistics that the USDA collects on the use of animals in the United States; nor are they covered under the Animal Welfare Act.

Q: Where do animals in biomedical research laboratories come from? A: The majority of animals in laboratories are purpose-bred (bred specifically to be used in experiments). People who sell purpose-bred animals are categorized by the U.S. Department of Agriculture as class A dealers.

Some of the dogs and cats used in laboratories are purchased from brokers known as class B dealers, who acquire the animals at auctions, from newspaper ads, or from various other sources including some animal shelters (a practice known as "pound seizure"). Pound seizure laws vary from state to state with a few states requiring shelters to give up their animals for used in experiments and some prohibiting the seizure of shelter animals for research. Some states have no laws at all, leaving it up to the individual shelter or locality.

Finally, some animals used in experiments are taken from the wild—including monkeys, mice, rats and birds.

Q: What happens to the animals when an experiment ends?A: The majority of the animals used in experiments are euthanized (killed) during or after the experiment. There are no accurate statistics available on exactly how many animals are euthanized in laboratories every year.

In some cases, animals are not euthanized, but die as a result of the experiment for which they were used. For example, the LD50 (lethal dose 50) test involves determining the dose of a substance that kills 50 percent of the animals tested. Some animals in laboratories, depending on the research protocol, can be used in additional experiments.

It is extremely rare that animals are either adopted out or placed into a sanctuary after research is conducted on them. In 2000, however, a national sanctuary system was established for chimpanzees who were used in research.

Q: What is the position of The HSUS regarding animals used in biomedical research? A: As do most scientists, The HSUS advocates an end to the use of animals in biomedical research that is harmful to the animals. Accordingly, we strive to decrease and eventually eliminate harm to animals used for these purposes. Our concern encompasses all aspects of laboratory animal use, including their housing and care.

We carry out our work on behalf of animals used and kept in laboratories primarily by promoting research methods that have the potential to replace or reduce animal use or refine animal use so that the animals experience less suffering or physical harm. Replacement, reduction, and refinement are known as the Three Rs or alternative methods.) The Three Rs approach, rigorously applied, will benefit both animal welfare and biomedical progress.

Certain species, such as chimpanzees, cannot be kept humanely in laboratory caging and should not be used in harmful research given their highly evolved mental, emotional, and social features and their concomitant vulnerability to suffering from living in captivity in research settings. Consequently, we place high priority on these species being phased out of harmful biomedical research and being relocated to appropriate sanctuary facilities.

Q: Are there laws and that protect birds, mice, and rats bred for biomedical research? A: Rats, mice and birds bred for biomedical research are not covered by the Animal Welfare Act; nor are they counted in the annual USDA statistics on animal use in the United States. There are two main laws that apply to animals in laboratories: the Animal Welfare Act and the Public Health Service Policy on the Humane Care and Use of Laboratory Animals.

Q: What is being done to find alternatives to animal use?A: Federal funding for alternatives has historically been very low.

Some companies have put substantial resources into finding alternatives. In the context of animal research, "alternatives" include not only the replacement of animals altogether, but reduction in the number of animals used and refinement of research so that it causes less pain, distress and suffering. Therefore, there are a number of alternatives currently available and can include something as simple as housing social animals in pairs rather than individually.

Unfortunately, however, aggressive development and implementation of alternatives, particularly replacement alternatives, is a complex process and involves many obstacles. First, there must be enough funding and interest in the development of alternatives. Additionally, in some cases, an existing alternative must be validated—an expensive and time-consuming process—in order to be accepted by regulatory agencies and others; this is particularly true in regards to testing of chemicals and products.